This invention relates to a membrane blood oxygenator system, and more particularly, to a blood reservoir for use therein.
Membrane oxygenator systems typically use flexible and collapsible reservoirs to contain blood volume within the extracorporeal circuit. These reservoirs are multifunctional. They allow the storage of priming solution, contain excess fluid as a result of patient volume changes, and act as bubble traps for gaseous emboli. Collapsible reservoirs have the added feature of collapsing if accidentally pumped dry, so as to prevent the entry of air into the oxygenator system which might cause air embolism in the patient.
Present collapsible reservoirs are of a fixed maximum size. It is generally desirable for best bubble removal and easiest operation to maintain the reservoirs completely full. In opposition to this, it is generally desirable to use a minimum volume of priming solution in the system in order to limit patient blood dilution or to limit the amount of blood needed to prime the system. Excessive blood dilution can adversely affect the patient's hematocrit level while excessive amounts of blood increase the possibility of transmitting hepatitis to the patient. The relative balance between best bubble removal and minimum priming volume varies with patient size, conditions during the operation, and operator technique. Changes in operating conditions include occasional large increases in blood volume due to the surgeon's removal of blood from the incision site. In order to satisfy all conditions, a variety of fixed reservoir sizes would be required. However, this still would not allow for changes occurring during the operation.
It is therefore an object of this invention to provide a universal reservoir which can be used under varying conditions.
The foregoing and other objects of this invention will be apparent from the following description and appended claims.